id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	launchpad_bug
378	"setup.py: which ""Twisted"" distribution name should we depend on?"	warner	warner	"We've learned a bit today about the overzealous downloading/installation of
Twisted by our setup.py on platforms that supposedly already have it
installed.

The entry in our setup.py (really _auto_deps.py) stanza that declares which
other packages we depend upon refers to a setuptools ""Distribution"" (which is
equivalent to a debian package). These distribution names are not case
sensitive, and one can use either hyphens or underscores to separate the
words. For example, ""twisted-core"", ""Twisted-Core"", and ""Twisted_Core"" are
all equivalent.

When Twisted-8.0.1 is built by running 'python setup.py install' on the
top-level setup.py, it produces a single .egg directory (i.e. a single
""distribution"", named ""Twisted"".

When Twisted-8.0.1 is built by running 'setup.py install' on each individual
subproject's setup.py, it produces a separate .egg directory for each
subproject: Twisted-Core, Twisted-Web, etc. This is how debian/sid current
does it. In sid, the 'python-twisted' debian package is a metapackage that
depends upon 'python-twisted-core', 'python-twisted-web', etc. It does not
contain any .egg directories. So if you have debian sid, you have the
""Twisted-Core"" distribution, but not the ""Twisted"" distribution. The most
recent debian release (""etch"") has twisted-2.4.0, but no .egg files.

Ubuntu feisty and gutsy have Twisted-2.5.0, and have just the single
""Twisted"" distribution. Dapper has Twisted-2.2.0, but does not have any .egg files.

Hardy has Twisted-2.5.0, and its ""python-twisted-core"" Deb package provides the ""Twisted"" distribution name.

The extra download/installs we've been seeing are because the tahoe setup.py
declares a dependency upon ""Twisted"", whereas the debian packages installed
on the system provide ""Twisted-Core"". The setuptools dependency language
doesn't provide for boolean-or, so we can't declare a dependency upon one or
the other.

So we need to decide what to do in the Tahoe setup.py:

 * depend upon ""Twisted"": builds on Feisty, Gutsy, and Hardy will not
   download anything extra, and will use the system Twisted instead. Builds
   on debian etch and sid will download Twisted-8.0.1 and install it into
   support/lib .
 * depend upon ""Twisted-Core"": builds on debian sid will not download
   anything extra. Builds on debian etch, and on ubuntu feisty/gutsy/hardy
   will download and install Twisted-8.0.1 .
 * modify our dependencies based upon whether
   {{{pkg_resources.require(""Twisted"")}}} succeeds or not. We could choose
   one of the two options above as our default, but then say that a system
   that provides ""Twisted"" will depend upon ""Twisted"" rather than
   ""Twisted-Core"", or vice-versa. This would avoid extra downloads on
   debian sid and ubuntu feisty/gutsy/hardy (i.e. all platforms on which
   the system Twisted has .egg_info data). However it would raise the
   question of what dependencies should wind up in the record on pypi.

I think Foolscap will need to make the same decision.

"	task	closed	major	1.1.0	packaging	1.0.0	fixed	setuptools